The present application claims the priority under 35 U.S.C. xc2xa7 119 of German Patent Application No. 196 54 434.3 filed on Dec. 30, 1996, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The present invention relates to a machine for manufacturing a continuous web, in particular a paper or cardboard web.
2. Discussion of Background Information
Machines of this type typically include a plurality of rolls such as press rolls, drying cylinders, suction rolls or the like.
Machines of the type mentioned above are known. In the manufacturing of continuous webs, a number of rolls are used, for example: press rolls, drying cylinders, or suction rolls. The web is guided over the surface of the rolls with the aid of at least one transport belt, which is also denoted as a screen or felt. It is also known that at high speeds of operation, for example from over 1000 m/min to more than 2000 m/min, that the tendency of the web to adhere to the surface of the rolls of a manufacturing machine leads to web tears. At any rate, the quality of the finished web is negatively affected by the adhesion tendency.
According to the present invention, a machine has been developed for manufacturing a continuous web that does not exhibit the above-noted disadvantage.
This is accomplished by such a machine that includes a plurality of rolls, such as press rolls, drying cylinders, or suction rolls. The web is guided over the surface of the rolls by at least one transport belt. At least one screen, such as a metallic screen, is guided between the web and the respective roll surface. The metallic screen may be made either completely out of steel or other metal or formed as a metallized drying screen. Moreover, it is possible to form the screen of metal and synthetic threads. By guiding the screen between the web and the surface of the rolls, the adhesion tendency of the web is reduced. The embodiments that are referred to in the following generally use a metallic screen of the kind mentioned previously. In view of the above, the metallic screen of the present invention may consist essentially of metal.
A preferred embodiment of the machine is characterized in that a separate metallic screen is assigned to one, several, or all the rolls. In such an embodiment, a relatively uncomplicated screen construction is possible, so that construction expenditures can be reduced or limited.
Furthermore, a preferred embodiment of the machine is characterized in that the metal screen is usable in a drying section, in which the web, with the aid of at least one transport belt, is guided around one or more rolls that are designed as drying cylinders. Since the metal screen is guided directly on the surface of the drying cylinder or cylinders, an adhesion of the web to this surface is safely avoided.
Another preferred embodiment of the machine is one in which the metal screen is usable within the press section, in which the web, with the aid of at least one transport belt that is designed as a press screen, is guided over one or more rolls that are designed as press rolls. Other aspects of the present invention include, e.g., that a separate metallic screen may be assigned to at least one of the rolls; that each metallic screen may be guided such that the web is guided as it runs off the surface of a roll in a defined manner; that the surface of the metallic screen may be very finely structured; that the metallic screen may be porous; that the metallic screen can be heated, preferably shortly before the contact of the web; that at least one cleaning device may be provided for the metallic screen; and, that the metallic screen may have a thickness of less than approximately 1 mm, preferably less than about 0.1 mm.
Furthermore, the machine with the metallic screen in accordance with the present invention may be usable in a drying group of the machine, in which the web, with the aid of at least one transport belt, is guided around the rolls, which are designed as drying cylinders, and also, in which the web is guided through rolls that are designed as press rolls, where at least two of the press rolls define a press opening therebetween. The web and the metallic screen may be guided through one press opening or through two press openings.
According to another aspect of the present invention, the machine for manufacturing the continuous web includes a plurality of rolls, and at least one screen guided between the web and surfaces of the plurality of rolls. The machine may include a separate screen assigned to at least one of the rolls, and each screen may be guided such that the web is guided as it runs off the surface of a roll in a defined manner.
In accordance with a further aspects of the invention, at least one of the screens has a very finely structured surface, and, at least one screen is porous.
Additionally, the machine in accordance with the present invention may further include a heater positioned adjacent the screen, and may be located before a web contact point of the screen. The machine may also include at least one cleaning device for the screen. Other aspects of the present invention may include, e.g., the screen having a thickness of less than approximately 1 mm, preferably being less than about 0.1 mm.
Furthermore, the machine with the screen in accordance with the present invention may be usable in a drying group of the machine, in which the web is guided around the rolls, which may be designed as drying cylinders, and also in which the web is guided through rolls that are designed as press rolls, where at least two of the rolls define a press opening, or nip, therebetween. The web and the screen are guided through one press opening or through two press openings.
As noted above, the screen may be made of metal, or formed as a metallized drying screen. Moreover, it is possible to form the screen of metal and synthetic threads.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.